Investments - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Total investments	$ 183.7	$ 184.7
Partnership Interests in Private Equity Funds
Schedule of Investments [Line Items]
Total investments	10.9	11.5
Investments, fair value	9.3	9.2
Equity method investments, fair value	1.6	2.3
Seed Capital Investments [Member]
Schedule of Investments [Line Items]
Total investments	$ 26.3	$ 26.1